Brazing flux



?atented June 11, 1929.

UNITED STATES PATENT oi-"sicar I d'OHN J. PH ELAN, F TROY, NEW YORK, .ASSIGNOR IO GENERAL ELECTRIC COMPANY, i A CORPORATION OF NEW YORK.

BRAZING FLUX.

No Drawing.

The present invention relates to a brazing flux and more particularly to a flux adapted to be employed in brazing chromium alloys such, for example, as iron-chromium and iron-nickel-chromium alloys. Heretofore it has been extremely difiicult to braze such ma terials owing to the tendency of the chromium alloys to oxidize and thus 1prevent the brazing material from wetting t e surfaces of the 1 structures to be brazed. It is one of the ob- 'ects of the present invention to provide. a razing flux which is of general utility and suitable for use not only in brazing chromium alloys but in brazing or soldering other 1 metals such as copper and iron if desired.

In carrying the invention into effect, I employ a mixture consisting of varying amounts of an alkali acid fluoride and an alkali tetraborate depending on the materials to be brazed. For example, in brazing chromium alloys, a very'satisfactory result is obtained by employing a flux containing above 50 to 60% by weight of potassium acid fluoride (KHF and about 50 to 40% by weight of potassium tetraborate(K B,O,).

If metals other than chromium alloys are to be brazed the composition of the flux may be further varied. In brazing copper and iron,

for example, I have employed a flux consisting of about 25% potassium acid fluoride with about 75% potassium tetraborate and obtained very good results.

In preparing the flux, the fluoride and borate powders are mixed with enough water to 5 form a paste which is applied with a brush,

and asa thin film to the surfaces to be brazed.

The surfaces thus treated are then heated to a temperature high enough to melt commercial silver solder, which is ordinarily employed 40 as the brazing metal. The molten solder flows onto the surfaces coated with the flux and makes a-very firm joint therewith. In

the brazing operation, I have found it ad- Applieatiolt flled June 19, 1928. Serial No. 286,715.

above. I have found however that the best otassium acid potassium tetra orate are emresults are obtained when fluoride and Pl y lVhileI have employed the present flux in silver brazing chromium allo s, the invention is not limited to the use of si ver as the brazing material. For example, steel dies containing'about 2% carbon and about 12% chromium have been copper brazed. In this case the die was cop er plated to prevent loss of the carbon, the ux applied to the surfaces to be brazer, and the structure copper brazed in a hydrogen atmosphere in the usual manner, providing a very rm brazing joint.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. A brazing flux consisting of at least 25 potassium acid fluoride and at least 40% potassium tetraborate.

2. A brazing flux containing about potassium acid fluoride and about 40% potassum tetraborate. v

3. A brazing flux containing about 25% to about 60% alkali acid fluoride and about to about 40% alkali tetraborate.

4. A flux containing about 25% to about so 60% alkali acid fluoride and about '7 5% to about 40% alkali borate.

In Witness whereof I have hereunto set my hand this 16th day of June, 1928.

JOHN J. PHELAN.

CERTIFICATE or CORRECTION.

Patent No. 1,717,250. Granted June 11, 1929', to

' JOHN J. PHELAN.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1, line 22, for the word "above" read "about", and line 66, same page, for "brazer" read "brazed"; and that the said Lettera' Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 30th day of July, A. D. 1929.

M. J. Moore, (Seal) Acting Commissioner of Patents.

CERTIFICATE 0F CORRECTION.

Patent No. 1,717,250. I Granted June 11, 1929, to

JOHN J. PHELAN.

it is hereby certified that error appears in the priiited specification of the above numbered patent requiring correction as toilows: Page 1, line 22, for the word "above" read "about", and line 66, same page, for "brazer" read "brazed"; and that the said Letters Patent should he read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 30th day of July, A. D. 1929.

M. -J. Moore, (Seal) Acting Commissioner of Patents. 

